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Arab Journal of Nuclear Sciences and Applications, 45(2)169-178 (2012) 

Bioleaching of Uranium - bearing material from Abu Thor area, West 

Central Sinai, Egypt for recovering uranium. 

Galal Mahmoud AbdEl Wahab , Maisa Mohamed Amin and Sami Kotb Aita 

Nuclear Materials Authority, P.O. Box 530 El Maadi, Cairo, Egypt. 

Rona82007@gmail.com 

ABSTRACT 

A uranium-bearing material was recorded within the Intra-Carboniferous 

Paleokarst Profile of Um-Bogma Formation at Abu Thor area, West Central Sinai, 

Egypt. The present paper is concerned with the bioleaching of U and Cu using 

Aspergillus Niger (A. Niger) followed their proper recovery. The working Abu Thor 

representative sample assays 0.22% U as the element of interest as well as up to 25% CuO 

beside the other rock constituents SiO2 (33%), Al2O3 (10.4%) and CaO(8.5%). The effective 

bioleaching of U and Cu from Abu Thor ore sample using A.Niger was performed at the 

following optimum conditions: an incubitation time of 6 days, sample/ liquid (S/L) ratio of 

1/10, pH value of 1 and a temperature of 60 º C. 

The prepared bioleach liquor assays 0.19 g/l of U and 15.8 g/l of Cu with leaching 

efficiencies of 97% and 79%, respectively. Uranium was recovered using 25% TBP in 

kerosene at O/A ratio of 1/1 and contact time of 5 min with achieved extraction 

efficiency of 96%. However the stripping of U was conducted by using 8% Na2CO3 at 

A/O ratio of 1/1 and contact time of 5 min with stripping efficiency reached 99%. On 

the other hand, Cu was directly precipitated as CuS using the freshly released H2S gas 

with the addition of solid Na2S. The optimum precipitation conditions were S/L ratio of 

1/100, pH1.5 and room temperature where the precipitation efficiency of Cu achieved 

99%. 

1-INTRODUCTION 

The origin of uranium mineralization of Um-Bogma Formation in West Central Sinai was 

reported by many authors the most important of them: Hilmy and Mohsen, (1965) (1) , El Reedy et 

al.,(1988) (2) , Dabbour and Mahdy, (1988) (3) , El-Sharkawi et al., (1990b) (4) , Hussein et al., (1992) 

(5) , Aita, (1996) (6) and Abd El Moneim et al., (1997) (7) . Recently Mira and Aita, (2009) (8) 

postulated that, the Carboniferous stratabound U and Cu mineralization in the form of copper 

carbonate, chloride, silicate, sulfate and phosphate minerals of super gene origin has been 

concentrated by pedogenic processes and latosol formation. 

Bioleaching processes are the ability of microorganisms (bacteria and fungi) to transform solid 

compounds into soluble and extractable elements and which can then be easily recovered. 

Bioleaching and bio-oxidation processes have been commercially applied for the recovery of copper, 

gold and uranium for two decades. In the near future, Turkish copper, gold and uranium mines will 

probably use these processes as commercial applications due to the economical and environmental 

reasons. In addition to lab tests, full scale feasibility studies to determine the impacts of climate and 

environmental factors for potential bioleaching in the mining areas will also be completed in the near 

future (Akcill, 2004) 

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(9) . 

Bioleaching is a new trend for leaching and processing operations of ground ore. These trends are 

likely to continue as new techniques and are developed in the future depending of course on the type 

and grade of the deposits as well as the uranium price. A. Niger is one of the most widely used fungi 

in the bioleaching applications and has many advantages over bacterial leaching, including the ability 

to grow under higher pH and faster leaching rate. This fungus has also been used in the production of


organic acids as citric, oxalic, acetic and glycolic acids (Gu and Wong, 2007) (10) . Organic acids are 

well known lixiviates for bioleaching of heavy metals from ore materials and solid wastes (Hefnawy 

et al., (2003) (11) , Mulligan et al.,2004) (12) . A. Niger was effectively used in U and Cu leaching of the 

Gibbsite minerals collected from west central Sinai, Egypt and assayed 0.12% of U and 0.7% of Cu. 

The maximum leaching efficiencies were 82 and 76%, respectively at the optimal conditions, 

(Yossef, 2007) (13) . 

Several studies have been published about the recovery of U from different ore materials 

especially from Sinai area these include: Amer, (1997) (14) who has been able to recover 99% of U 

from the sulfate leach liquor of the uraniferous Paleozoic sedimentary rocks of Abu Thor area 

assayed 0.312% of U using Trioctyl amine, (TOA) organic solvent. Cecal et al., (2005) (15) studied 

the feasibility of bacterial recovery of U from the low grade black schist's occurring in the Okcheon 

district, South Korea. Following the introduction of Acidithiobacillus ferrooxidans, 80% of U could 

be extracted from the schists, which contain 0.01% U3O8 by weight, within 60 h at a pulp density of 

100 g-ore/l. Only 18% of U was extracted without the microbial activity. Uranium leaching 

efficiency was not greatly affected by the addition of Fe 2+ in the range of 5–9 g/l, and the leaching 

efficiency of U from this schist’s by A. ferrooxidanscould can be efficiently maintained at high pulp 

densities (up to 500 g-ore/l). 

In the present work, a new technique has been performed depending mainly upon precipitation 

of the main interfering elements such as: Zn, Pb and Cu directly using freshly prepared H2S gas. The 

bioleach liquor free of these interfering elements was then directly subjected to precipitation using 

NaOH at pH11 and the obtained precipitate was dissolved with 3% HNO3 solution to be suitable for 

the recovery of pure U salt using TBP. 

2-EXPRIMENTAL 

2.1. Sampling 

A representative sample weighting 50Kg was collected from the upper organic -rich mudstone 

sub horizon of the latosol horizon of Abu Thor area by Mira and Aita, (2009) (8) according to the 

geological map shown in Figure (1). The collected sample consists mainly of alternating multi 

colored layers of kaolinitic black to green shale, ochres and nodules of alunite and gypsum together 

with the copper and uranium minerals. The later are mainly present as lenticular masses of up to 

40cm long and 10cm thick as well as discrete pockets up to 20cm in diameter beside some streaks, 

veinlets and spots that are also recorded. 

2.2. Materials and Sample Characterization. 

A. Niger was isolated from the black shale ore in Wadi Nasib area, South Western Sinai, Egypt 

and used in the bioleaching of the ore sample . The medium used was Dox liquid of the following 

composition (g/l):1NaNO3, 2 KH2PO4, 1Mg SO4.7 H2O, 0.5 KCl, 0.5 FeSO4.5 H2O and trace of 

sucrose. The pH value of the medium was adjusted at 6.5 before autoclaving at 1.5 atmospheres. for 

20 min. A weight of 0.5g of the ore sample ground to a particle size less than 0.25mm was 

completely dissolved by using the acid mixture (H2SO4, HCl and HF) and directed to different 

analysis methods for determining its chemical composition. Both the major elements (Cu, Al, Zn, Fe) 

and the trace elements (Mn, V, Pb) were determined using the flame atomic absorption, (FAA) 

Unicam 969 at the proper wavelengths. While U was analyzed by titration against NH4VO3 (Daveis 

and Gray, 1964) (16) , Si was analyzed by UV spectrophotometer at ?640nm with molibedate method. 

The flame photometer (Sherwood Model 410) was used for the determination of both Na and K. In 

addition, the elemental relative concentration of the final U product was identified using (EDAX- 

SEM), PHILIPS and the product of Cu was identified using XRD technique PHILIPS, The pH value 

of the aqueous solutions were adjusted with a pH meter (Digimed DM-21). 

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2.3. Optimization of bioleaching parameters and recovery of Cu and U 

Bioleaching process upon the U and Cu bearing minerals of Abu Thor area was performed using 

A.Niger. The different bioleaching affecting factors such as: incubation period, (1-10 days), solid / 

liquid (S/L) ratio, (1/2 - 1/20), pH value (1- 8) and temperature, (25-100ºC) were investigated. The 

recovery of Cu was carried out by direct precipitation using the freshly released H2S while U was 

recovered and purified using 25% TBP in kerosene. 

Figure (1): Geological Map of Abu Thor Locality (Mira and Aita, 2009) 

3.1. Mineralogical and chemical composition 

3-RESULTS &DISCUSSION 

According to Mira and Aita (2009) (8) the mineralogical analysis of Abu Thor collected sample 

revealed the presence of different U and Cu minerals such as: zippeite, 

(K4(UO2)4(SO4)4(OH)10.4H2O) [Card No.,8-138], atacamite ,(Cu2Cl(OH)3) [Card No.,23-948], 

paratacamite (Cu2(OH)3Cl) [Card No.,23-947,] rosasite (Cu.Zn)2 CO3 (OH)2), [Card No.,17-216], 

calcite, (CaCO3 ) [Card No., 5-586], and dolomite, (CaMg(CO3)2. [Card No., 11-78]. On the other 

hand, the complete chemical analysis of the ore sample given in Table (1) revealed the presence of 

0.22% U, 25% CuO, 33% SiO 2 and10%, Al2O3. In the mean time, some trace elements have been 

analyzed including Pb (80ppm) and Ni (10ppm). 

3.2. Optimization of bioleaching parameters 

As was expected, it was revealed from the color and the analysis of the bioleach liquor that Cu 

in parallel to U was effectively co-leached with A. Niger. Thus, it was decided to take the bioleaching 

of Cu in consideration with the different bioleaching parameters such as: incubation period, solid / 

liquid (S/L) ratio, pH values and temperature. 

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Table (1): Chemical composition of Abu Thor U bearing material. 

3.2.1. Effect of the incubation period. 

Major oxides Conc., (%) Trace 

elements 

Conc., ppm 

SiO 2 33 Na 4500 

Al2O3 10 Mn 1500 

CuO 25 K 1000 

CaO 8.5 U 2200 

MgO 2 V 1500 

Fe2O3 2 Pb 80 

1.3 Ni 10 

TiO 2 

P2O5 

1.5 

ZnO 2 

Total ignition loss 11.6 

This factor was studied by putting 100 ml of the Dox liquid medium in six 250 ml measuring 

flasks which were autoclaved at 1.5 atm. for 20min. After cooling, the flasks were inoculated with 0.5 

ml of spore suspension of A-Niger and finally incubated at 30ºC for 7 days. The flasks which contain 

the culture filtrate were supplemented with the ore sample at S/L ratio of 1/10 at pH of 3.5 and at 60ºC 

and incubated in an orbital shaker at 100 rpm. Both U and Cu were daily determined until reached the 

equilibrium stage. Triplicate sets of the fla sks for each day. Results in Table (2) indicated that both U 

and Cu leaching efficiencies were highly affected by the incubation time where the maximum leaching 

efficiencies attained 64% and 74%, respectively after 6 days. It was noticed that after 8 days the 

leaching percentage of U and Cu have together decreased. This phenomenon may be attributed to the 

effect of some interfering metal ions especially Zn, Fe and Al that might dissolved. 

3.2.2. Effect of Solid / Liquid (S/L) ratio. 

The effect of S/L ratio was performed by the addition of the culture filtrate of A. Niger which 

previously prepared to the ore sample at different S/L ratios namely: 1/2, 1/5,1/7, 1/10 and1/20. The 

flasks were incubated for 6days in an orbital shaker at 100rpm for 2 0min and filtrated. Both U and 

Cu were analyzed and their leaching efficiencies were calculated and tabulated. It was noticed that 

the leaching efficiencies of the elements of interest increased by increasing S/L ratio. Where the 

leaching efficiency of U increased from 27 % to 74% and that of Cu increased from 21% to 64%, and 

then started to decrease, Table (3).This may be attributed to sufficient of organic acids produced by 

A. Niger to soluble Cu and U beside the interfering elements e.g. Zn, Pb . 

Table (2): Effect of incubation periods upon U and Cu bioleaching efficiency. 

Days 

Leaching efficiency,% 

U Cu 

1 25 30 

2 28 53 

4 51 72 

6 74 64 

8 57 68 

10 52 65 

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Table (3): Effect S/L ratio upon U and Cu bioleaching efficiency. 

S/L Ratio 


U Cu 

1/2 27 21 

1/5 41 27 

1/7 51 38 

1/10 74 64 

1/20 68 61 

3.2.3. Effect of pH values 

The acidity of culture filtrate of A. Niger is one of the most important factors affecting the 

bioleaching of the working sample. However the culture was adjusted at different pH values; 1, 2, 

3.5, 6 and 8 and mixed with the ore sample at S/L ratio of 1/10 at room temperature and incubated for 

6 days. The data shown in Table (4) emphasized that, the maximum leaching efficiencies of U and 

Cu, (87% and 77%, respectively) by culture filtrate of A. Niger was conducted by increasing the 

acidity of the culture filtrate up to pH1. It was found that, increasing the pH value of the culture 

filtrate has an opposite effect on the leaching efficiencies of Cu and U. This might be attributed to the 

role of medium acidity increase leads to more leaching of different elements. 

Table (4): Effect pH values upon U and Cu bioleaching efficiency. 

pH Values 

3.2.4. Effect of temperature. 

At the previous fixed conditions beyond varying the temperatures of culture filtrate of A. Niger 

from 25 ºC to 100 ºC. It was found that, both Cu and U leaching efficiencies increased by increasing 

temperature up to 60ºC where a subsequent decrease has been started. Results given in Table (5) 

indicated that, the maximum leaching efficiencies of both U and Cu (97% & 79%) were recorded at 

60ºC. The obtained results might be attributed to both autotrophic and heterotrophic microorganisms 

that are able to release Cu from chalcopyrite at temperature range from (60ºC - 80ºC) (Rossi, 

1990) (17) . Also, the rate of extraction of Cu at the temperature of 60ºC is much faster and economic 

(pradha et al., 2008) (18) . 

Table (5): Effect temperature upon U and Cu leaching efficiency. 

Temperature, ? C 


U Cu 

1 87 77 

2 75 74 

3.5 74 64 

6 53 35 

8 16 13 


U Cu 

30 74 64 

40 79 74 

60 97 79 

80 85 67 

100 

62 

53 

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From the previous study, it could be inferred that both U and Cu from Abu Thor representative 

sample clearly respond to bioleaching applications using culture filtrate of A. Niger incubated in 6 days 

at S/L ratio of 1/10 and adjusted to pH1 at 60 ºC. 

3.3. Recovery of Cu and U 

By applying the optimum conditions upon 100g of the ore sample yielded leach liquor contains 

0.19g/l U and 15.8g/l Cu with leaching efficiencies 86% and 79%, respectively. Also, the chemical 

analysis of the bioleach liquor revealed the presence of 0.63g/l Fe and 0.8g/l Zn with leaching 

efficiencies 45%and 56%, respectively. Copper was recovered from the bioleach liquor by direct 

precipitation with the addition of solid Na2S at pH value =1.5 due to the lower value of its solubility 

product with S -- anions namely: (Ksp CuS= 6.3 x 10 -36 and ZnS 2.5 x 10 -22 Alexeyev (1973) (19) . On the 

other hand, U 6+ and Fe 3+ were reduced with S -- anion to U 4+ and Fe 2+ . 

3.3.1. Direct precipitation of Cu 

Copper and zinc were directly precipitated as CuS and ZnS from the bioleach liquor of the ore 

material sample containing 15.8 g/l Cu, 0.8 g/l Zn besides 0.19 g/l U using the freshly prepared H2S 

gas with the addition of solid Na2S. The precipitation optimum conditions of CuS and ZnS were S/L 

ratio of 1/100, pH1.5 at room temperature. Practically, about 10g of Na2S (assays 68%) was added to 

1000ml of the bioleach liquor at pH1.5 at room temperature. After filtration and washing a weight 

22g of CuS was recovered with precipitation efficiency achieved 99%. The product was identified by 

using both XRD and EDAX techniques Figures (2,3), respectively. The purity of CuS achieved 

97.9% with impurities of 0.9% Zn, 0.3% Pb, 0.5% Mn and 0.4%Na. 

U 6+ + Cu 2+ + S -- ? CuS ? + U 4+ . + S 

3.3.2. Solvent extraction of U 

Black ppt 

The bioleach liquor containing 0.19g/l U and free of Cu and Zn was directed to the solvent 

extraction unit to recover U using 25% TBP in kerosene. However, 1200 ml of this solution was first 

treated with pellets NaOH to precipitate U 4+ at pH11.5 with precipitation efficiency of 96.5%. After 

filtration and washing, the impure U precipitate was completely dissolved in 3% HNO3 to have 

uranyl nitrate solution of pH0.6 and assaying 0.18g/l U. This solution was then treated with 25% TBP 

in kerosene at an O/A ratio of 1/1 and shaken for 5min where U was completely transferred to the 

organic phase. The loaded solvent was scrubbed with 1.5% HNO3 at an O/A ratio of 1/20 to minimize 

the co-extracted impurities such as: Fe, V and Zn. 

A solution of 8% Na2CO3 was therefore used for the stripping of U from the loaded solvent at an 

A/O ratio of 1/2 for a contact time of 5min with achieved stripping efficiency of 95%. U in the strip 

solution was crystallized by gentle evaporation at 70ºC and the obtained product was analyzed with 

SEM. The EDAX chart of the precipitate emphasized that it assays 99.3% of U, Figure (4). All the 

obtained data have been formulated into a worked follow-sheet shown schematically in Figure (5). 

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Card No. 6-0464 

CuS 

CuS 

4-CONCLUSIONS 

A successful bioleaching process with the culture filtrate of A.Niger was applied for leaching 

Cu and U from the representative ore material of Abu Thor area,(0.22% U & 20% Cu), West 

Sinai, Egypt with achieved leaching efficiencies of 97% and 79%, respectively. The bioleaching 

optimum conditions involve an incubation period of 6 days, S/L ratio of 1/10, and pH value of1 

and bioleaching temperature of 60ºC. The prepared leach liquor assaying15.8 g/l Cu and 0.19 g/l 

U was then directed to the direct precipitation both Cu and Zn impurities using the freshly 

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CuS 

CuS 

Figure (2): XRD pattern of the prepared pure CuS 

Figure (3): EDAX chart of the prepared pure CuS 

Figure (4): EDAX chart of the prepared pure pure yellow cake


prepared H2S gas which released by the addition of solid Na2S to the leach liquor. The optimum 

precipitation conditions have been included S/L ratio of 1/100, pH1.5 at room temperature. The 

achieved recovery of Cu as CuS reached 99.3% with purity 97.9% and co-precipitated impurities 

of 0.9 % Zn, 0.3% Pb, 0.5% Mn and 0.4%Na. 

The filtrate containing 0.19g/l of U was directed to the solvent extraction unit for recovering 

U using 25% TBP in kerosene. The maximum U extraction efficiency optimum conditions were 

O/A ratio of 1/1 and contact time of 5min. On the other hand, the stripping process was 

performed using 8% Na2CO3 solution at A/O ratio of 1/2 and contact time of 5min gave the 

maximum U stripping efficiency of 95%. The EDAX chart of the precipitate emphasized that it 

assays 99.3% U with total recovery achieved 86.36%. 

100g ore sample 

Culture filtrate 

S/L 1/10, pH1, 60 ? C 

H2O 

Washing 

CuS 

Filtrate 

Bioleaching 

Filtration 

Solid Na2S 

Cu precipitation 

S/L 1/100, pH=1.5, RT 

Filtration 

ppt 

Filtrate/ pH11 

Pellets NaOH 

Conc HNO3/pH0.6 

8% Na2CO3 

U precipitation 

Filtration 

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ppt 

Dissolution 

25% TBP 

Stripping 

U crystallization 

Pure Yellow cake 

Residue 

Figure (5): A worked follow-sheet for the processing of Abu Thor representative sample.


5-REFERENCES 

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(2) El Reedy, M.W.; Mahdy, M.A.; El Aassy, I.E and Dabbour, G.A.,(1988): (( Geochemistry 

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(3) Dabbour, G.A. and Mahdy, M.A.,(1988) (( Mineralogical studies on the Carboniferous 

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(4) El Sharkawi, M.A., El Aref, M.M. and Abd El Motelib, A. 1990b: (( Syngenetic and 

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(5) Hussein, H., Abd El Monem, A., Mahdy, M., El Aassy, I. and Dabbour, G., (1992): (( On the 

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pp. 125-135. 

(6) Aita, S.K. (1996): (( Geological, mineralogical and geochemical studies on some radioactive 

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(7) Abdel Monem, A.; El Aassy, I.E.; Hegab, O., El Fayoumy, I. and El Agami, N.,(1997): 

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(12) Rawlings , D. E., (2004) (( Microbial assistant dissolution of minerals and its use in the mining 

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(13) Youssef, H.I., (2007) (( Bioleaching of some heavy metals from different ores, Egypt )) , PhD 

Thesis, Faculty of Agriculture, Ain Shams University, Egypt. 

(14) Amer, T. E., (2007) (( Geochemical and extraction of U, Cu and Mn from the ore materials of the 

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(16) Daveis , W. and Gray, W. A.,(1964) (( Rapid and specific titrametric method for the precise 

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chalcolpyrite ore by fungi )) Indian J. Exp Biol. 40 (3) pp 319-324. 

(18) Pradhan, N., Mohapatra, S., Mohanty, S.and Sulka, L. B., (2008) (( Recovery of lateritic 

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(19) Alexeyev, V.N., (1973) (( Qualitative Chemical Semi microanalysis )) , English translation, Mir 

Pub. 1980, pp. 210-215. 

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